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<Paper uid="P87-1031">
  <Title>Expressing Concern</Title>
  <Section position="3" start_page="222" end_page="222" type="intro">
    <SectionTitle>
4. Concerns and Expression
</SectionTitle>
    <Paragraph position="0"> In this section, we describe the problems that concerns were initially meant to address in plan failure detection. We also describe how this same process has been used to express potential plan failures to the user.</Paragraph>
    <Paragraph position="1"> KIP is a a commonsense planner ONilensky83) - a planner which is able to effectively use a large body of knowledge about a knowledge-rich domain. Such knowledge includes a general understanding of planning strategy, detailed descriptions of plans, the conditions necessary for these plans to execute successfully, and descriptions of those potential goal conflicts that the plans might cause. Due to the detailed nature of this knowledge, it is difficult to detect potential plan failures. Condition failures are hard to detect since there are many conditions for any particular plan. Goal conflict failures are difficult to detect since any of the many effects could conflict with any of the many goals of the user. Furthermore, many of the user goals are not inferred until a threat to user interest is perceived. Previous planning programs (Fikes71, Newel172, Sacerdoti74) searched exhaustively among every condition and every potential goal conflict for potential plan failure. This is a very inefficient process. On the other hand, human consultants generally consider only a few potential plan failures while assessing a particular plan.</Paragraph>
    <Paragraph position="2"> Additionally, KIP may not be aware of the values of many of the conditions of a particular plan. Most previous planning research assumed that the values for all the conditions is known. However, in UC, when a user describes a planning problem which is then passed to KIP, the values for many conditions are usually left out. All users would believe that normal conditions, like the machine being up, would be assumed by the consultant. A naive user might not be aware of the value of many conditions that require a more sophisticated knowledge of UNIX. An expert user would believe that the consultant would make certain assumptions requiring this more sophisticated knowledge of UNIX. It would be undesirable to prompt the user for this information, particularly for those values which axe not important for the specific plonning situation.</Paragraph>
    <Paragraph position="3"> Therefore, concerns were introduced in order to detect plan failures. Concerns allow KIP to use information about the likelihood and importance of potential plan failures. They allow the planning database designer to store knowledge regarding which conditions are most likely to be unsatisfied, and which goal conflicts are most likely to occur as a result of the execution of a particular plan.</Paragraph>
    <Paragraph position="4"> Furthermore, the same concern information can be used in order to determine which potential plan failures should be expressed to the user. When, KIP selects a potential plan, the concerns of that particular plan are evaluated in the particular planning situation. Once the concerns of a plan are evaluated there are three possible scenarios. In the first case, none of the concerns are important in the particular planning situation.</Paragraph>
    <Paragraph position="5"> The plan is generated to the user without any concern information. In the second case, there is a moderate degree of concern regarding the plan. In this case, the plan is generated along with the concern information. In cases where there is a high degree of concern, the plan is modified or a new plan is selected. These scenarios will be fully explained in the following section. Before describing KIP's algorithm regarding decisions about concerns, we first describe a simple example of the use of concerns. For the purposes of this example, we consider only condition concerns.</Paragraph>
  </Section>
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